1. Field of the Invention
The present invention relates to a screw driving gun, more particularly to a screw-belt advancing mechanism for a screw driving gun.
2. Description of the Related Art
Referring to FIG. 1, a conventional screw driving gun 2 (illustrated in phantom lines) generally includes a driving shaft 21, a belt-retaining mechanism 1, and a screw-retaining belt unit 3. The screw-retaining belt unit 3 includes a belt body 30, a plurality of screw 31 retained releasably on the belt body 30, and a plurality of engaging holes 32, each of which is disposed between adjacent two of the screws 31.
The belt-retaining mechanism 1 includes a sliding unit 10, a barrel unit 22, and a belt-retaining member 12. The barrel unit 22 receives the driving shaft 21 therein, and has a rear end connected to the screw driving gun 2, and a front end opposite to the rear end. The sliding unit 10 is connected telescopically to the front end of the barrel unit 22, is movable relative to the barrel unit 22 between extended and retracted positions, and includes a nose plate. An urging member 221 is sleeved on the driving shaft 21 and urges the sliding unit 10 to move to the extended position. The screw-retaining belt unit 3 is fed into the sliding unit 10 via a side opening 11 and is retained on the nose plate of the sliding unit 10 by the belt-retaining member 12, which is biased frontwardly in such a manner that an engaging end 120 of the belt-retaining member 12 engages a selected one of the engaging holes 32 in the screw-retaining belt unit 3 so as to retain the belt unit 3 on the nose plate of the sliding unit 10. The engaging end 120 of the belt-retaining member 12 is formed with an inclined lower sliding face 121 which is in sliding contact with the screw-retaining belt unit 3 so as to permit disengagement of the belt body 30 from the engaging end 120 of the belt-retaining member 12 during upward pushing of the screw-retaining belt unit 3 to a position, where a selected screw 31 is aligned with the driving shaft 21.
The aforesaid conventional screw driving gun 2 is disadvantageous in that it is inconvenient and laborious to pull the screw-retaining belt unit 3 manually in order to align a selected one of the screws 31 with the driving shaft 21.